If any
drive in the stripe set fails, the entire array will be lost. The focus with RAID 0 is one of
performance only. While RAID 1 does provide protection against drive failure, it does
nothing to optimize performance, because throughput is still limited to what one drive
can handle. RAID 1 is focused on data protection, not performance.
RAID 5 has long been the choice for the best mix between data protection and performance.
Data is striped across all disks, as it is with RAID. In addition, one parity stripe
is maintained as protection against loss of a drive. With that one parity stripe, a RAID 5
array can lose a single disk and continue to function. The remaining disks use their parity
information to infer what the missing data is (see Figure 10-5).
Of course, if there is a disk failure, the culprit should be replaced as quickly as possible.
Most controllers supporting RAID 5 will rebuild the array on the fly. While the RAID 5
array is down a disk or in its parity-rebuilding phase, loss of an additional disk would
mean a loss of the entire array.
Figure 10-5. RAID 5 allows for the loss of one drive while keeping the data array operational.
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